• Reconstruction des fibres blanches cérébrales à partir de la dissection et recalage dans l'IRM post-mortem pour la comparaison à la tractographie cérébrale par IRM de diffusion ( PDF , 36792692 kB )

The knowledge of the morphology of white matter fiber tracts, which connect distant cerebral areas, is essential to better understand brain functions. Diffusion MR tractography indirectly reconstructs this anatomy using complex mathematical algorithms. After a review of the existing methods for tractography validation, we propose an original method based on 3D reconstruction of dissected tracts. Our method, FIBRASCAN, used iterative surface acquisitions during dissection. The tracts were segmented on each surface and then reconstructed by stacking these surfaces. A rigid support allowed registration between surfaces and then registration to MRI. We demonstrated the accuracy of each reconstructing step, and the feasibility of our method on several tracts. In the last part of this work, the structure of white matter fibers and the changes induced by preparation and dissection were investigated using electron microscopy. We showed that dissection preserves the structure of axons and can thus be considered as a validation tool for tractography.The knowledge of the morphology of white matter fiber tracts, which connect distant cerebral areas, is essential to better understand brain functions. Diffusion MR tractography indirectly reconstructs this anatomy using complex mathematical algorithms. After a review of the existing methods for tractography validation, we propose an original method based on 3D reconstruction of dissected tracts. Our method, FIBRASCAN, used iterative surface acquisitions during dissection. The tracts were segmented on each surface and then reconstructed by stacking these surfaces. A rigid support allowed registration between surfaces and then registration to MRI. We demonstrated the accuracy of each reconstructing step, and the feasibility of our method on several tracts. In the last part of this work, the structure of white matter fibers and the changes induced by preparation and dissection were investigated using electron microscopy. We showed that dissection preserves the structure of axons and can thus be considered as a validation tool for tractography.Autism is a developmental disorder of the central nervous system defined by impairments in social interaction and communication, and by restricted and repetitive behavior. Its prevalence is currently estimated at around 1% in the general population. Autism is characterized by a wide heterogeneity at both phenotypic and genetic level. To date, more than 300 candidate genes were characterized either by copy number variations (CNV) and/or nucleotide variations (SNV). Their identification has highlighted a significant contribution of de novo mutations, as well as the involvement of targeted pathophysiological pathways, particularly post-synaptic density (PSD).

• Dates
  Created on June 26, 2015